Light or low molecular weight olefins such as ethylene and propylene, for example, serve as feeds for plastics production and for the production of petrochemicals which serve as feeds for plastics production. The demand for light olefins has been steadily increasing and will continue to increase dramatically. Light olefins have traditionally been produced through the process of steam or catalytic cracking. Paraffin dehydrogenation is an alternative source of light olefins. However, the demand for light olefins is outstripping the capacity of traditional sources of light olefins.
It has been recognized that due to environmental concerns and newly enacted rules and regulations, saleable products must meet lower and lower limits on contaminants such as sulfur and nitrogen. Recently new regulations require the essentially complete removal of sulfur from liquid hydrocarbons which are used in transportation fuels, such as gasoline and diesel.
Aromatic compounds such as benzene, toluene and xylene are valuable petrochemical components. The xylene isomers are produced in large volumes from petroleum as feedstocks for a variety of important industrial chemicals. The most important of the xylene isomers is paraxylene, the principal feedstock for polyester which continues to enjoy a high growth rate from a large base demand. Orthoxylene is used to produce phthalic anhydride. Metaxylene is used in such products as plasticizers, azo dyes and wood preservers. Neither the xylenes nor benzene are produced from petroleum by the reforming of naphtha in sufficient volume to meet demand and conversion of other hydrocarbons is necessary to increase the yield of aromatic compounds including xylenes and benzene.